1. Field of the Invention
The present invention relates to a signal input system to perform the transmission and the reception of a signal between source equipment and sink equipment.
2. Description of Related Art
In recent years, a standard called as High Definition Multimedia Interface (HDMI) which is the standard of expanding Digital Visual Interface (DVI), has been put to practical use. HDMI can transmit an image signal and a sound signal that take digital form and are not compressed in a plurality of formats.
However, a conventional signal input system has a problem of an excessive long time from the connection of a piece of source equipment with a piece of sink equipment to the display of an image on the sink equipment side.
To put it concretely, in order to output an image and the like in the conventional signal input system, the connection of both the pieces of equipment is first detected on the basis of a hot plug signal transmitted through a hot plug line. After that, the sink equipment transmits extended display identification data (EDID) indicating the format and the like of an image signal that the sink equipment deals with, to the source equipment. The EDID is the data indicating the formats of the image signal in the sink equipment (for example, the display resolution thereof, the image frame period thereof, and the signal format thereof) and the formats of a sound signal (for example, the number of sample bits thereof, the sampling frequency thereof, and the signal format thereof), and is subjected to transmission and reception through display data channel (DDC) lines. Then, the source equipment converts the image signal into a predetermined format on the basis of the received EDID, and transmits the image signal to the sink equipment together with info information. On the other hand, the sink equipment sets an image IC and the like on the basis of the info information transmitted from the source equipment, and then releases muting. The image display based on the image signal transmitted from the source equipment is thus started.
For example, Japanese Patent Application Laid-Open Publication No. 2002-247474 discloses a display control apparatus to receive the information of display resolution from a television monitor by examining the voltage level of a signal through an image terminal, and can automatically perform the optimum display using a region of the monitor in which a display can be performed by performing the display according to the resolution.
According to the Japanese Patent Application Laid-Open Publication No. 2002-247474, the display resolution can be detected on the basis of the voltage level of the signal from the image terminal in place of the EDID.
However, even when the technique of the Japanese Patent Application Laid-Open Publication No. 2002-247474 is applied to the signal input system performed by the source equipment and the sink equipment connected to each other with an HDMI cable, the source equipment and the sink equipment detect the mutual connection with the HDMI cable; after that, the display resolution of the image signal is detected on the basis of the voltage level of the signal from the image terminal; and the setting of the image IC and the like are then performed on the basis of the detected display resolution. No images can be output until the above processing has been performed, and consequently the problem of the delay before the display of an image still remains.